Extended Abstract (428K)1.2
Dynamics of convective lines with leading precipitation
Matthew D. Parker, Colorado State University, Fort Collins, CO
Mesoscale convective systems account for a disproportionate number of flash floods, and the amount of flooding that they cause is related to their organizational modes and speeds. Recent work has identified three kinds of linear convective systems: those with convective lines and either trailing, leading, or parallel precipitation, the latter two of which have received comparatively little study. I will present work in which I've used idealized numerical simulations to address the dynamics governing individual air parcels' accelerations within convective lines with leading precipitation. It appears that, even though it is unconventional, a system with inflow passing through its line-leading precipitation can still be stable and long-lived. Some findings include that, contrary to expectations, inflowing air that passes through the pre-line precipitation in these systems is actually destablized by the vertical profile of evaporative cooling and by lifting. In addition, although relatively strong wind shear in the middle and upper troposphere accounts for a component of the downshear accelerations of air parcels in the simulated updrafts, a mature system with leading precipitation also renders both persistent and periodic pressure anomalies that contribute just as much to the downshear accelerations. Many of these accelerations, which govern the overall system structure, are largely transient and are lost when averaged over multiple convective cycles. Therefore, my oral presentation and preprint article will incorporate parcel-based analyses of the relevant physical processes which contribute to and maintain the convective line with leading precipitation structure.
Session 1, Mesoscale Convective Systems I
Monday, 12 August 2002, 10:30 AM-12:00 PM
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